Reconfigurable saws of various kinds are well-known in the art, as evidenced by the following United States patents:
The incorporation of a pivotable arm into a hacksaw frame is disclosed in U.S. Pat. Nos. 2,309,816 and 5,471,752, and the following U.S. patents provide a variety of blade-tensioning arrangements:
Additional forms of saws are disclosed in the following U.S. patents:
Among the foregoing, particular note may be made of Duffy U.S. Pat. No. 4,680,863. Duffy describes a saw in which the blade can be disposed either parallel to the back member or in a number of angular relationships thereto, such variation being achieved, in part, by rotating one of three fingers into operative position.
The saw provided by Duffy would however appear to suffer from several significant drawbacks. First of all, because a plurality of laterally stacked fingers are employed the limited space available requires each finger to be relatively thin and, therefore, to be relatively weak. The thinness of the fingers also precludes the provision of blade-mounting elements on opposite sides thereof, such as to enable orientation of the blade both parallel to a medial plane of the frame and also at an angle thereto, as is conventional (typically at an angle of 45xc2x0) and desirable. Moreover, because the fingers are spaced in different lateral planes the mounted blade must (at least when either of two of the three fingers are used) extend at an angle to the medial plane; albeit relatively small, such angular displacement would preclude accuracy of cutting (unless the saw itself were held at an artificial angle to the workpiece). Finally, because forward blade-engagement elements are provided only on the fingers of the Duffy saw, the blade must be displaced from the back member in all configurations, and minimal spacing capability cannot therefore be achieved.
Accordingly, it is a broad object of the present invention to provide a saw frame assembly that enables ready tensioning and release of the mounted blade, coupled with facile conversion between either of two configurations, one of which configurations is diminished from the other to enable cutting within relatively confined spaces.
Other objects of the invention are to provide such a frame assembly which enables orientation of the mounted saw blade both parallel to a medial plane and also at an angle thereto, which assembly is of strong, durable construction, is practical and economical to manufacture, and is comfortable and convenient to use and to operate for quick and easy conversion.
It has now been found that certain of the foregoing and related objects of the invention are attained by the provision of a saw frame assembly which includes a generally planar frame comprising a back member, handle structure, and a single, elongate arm member. The arm member is substantially nonremovably mounted on the forward end portion of the back member for movement between a first position, in which it extends downwardly from the back member in generally confronting, coplanar, spaced relationship to the handle structure, and a second position in which it extends generally along the back member. A first pair of substantially transversely aligned blade-engaging elements are provided on opposite sides of a distal end portion of the arm member, and a second pair of such elements are provided on the opposite sides of a forward end portion of the back member. A quick-release blade-tensioning mechanism is mounted on the frame, and is constructed to effect displacement of a movable member between blade-tensioning and blade-releasing positions, the movable member having a third pair of such blade-engaging elements on opposite sides thereof. Each of the blade-engaging elements is constructed to engage one end of a removably mounted saw blade, and the first and second pairs thereof are commonly disposed on an arc circumscribing the third pair, at least in the blade-tensioning position of the movable member. One element of each pair of blade-engaging elements lies substantially in a first lateral plane, disposed to one side of the medial plane of the frame, and is constructed to orient a mounted blade substantially parallel to the plane, and the other element of each pair lies in a second lateral plane, disposed to the opposite side of the medial plane, and is constructed to orient the mounted blade at a substantial angle to the plane. In one configuration of the frame assembly a saw blade is mounted (in either of the two orientations enabled) between the second and third pairs of blade-engaging elements, for cutting within a relatively confined space, and it is readily converted for mounting the blade between the first and third blade-engaging elements, for cutting within a relatively open, unconfined space.
The arm member will usually be substantially rectilinear and pivotably mounted on the back member of the frame, with abutment elements cooperatively defining a limit of its lowered, operative position. The forward end portion of the back member will advantageously define an upwardly opening channel in which the arm member is disposed in its inoperative position. Each of the blade-engaging elements will typically comprise a permanent pin or stud that projects normal to an orienting, blade-supporting surface of the mounting structure.
In especially preferred embodiments of the assembly the handle structure of the frame will provide a cam bearing surface, and the blade-tensioning mechanism will comprise a lever-form of operating member and a turnbuckle arrangement. A cam element on the operating member will engage the cam bearing surface and cooperate therewith to effect displacement of a movable member on which the third pair of engagement elements is provided, and the turnbuckle arrangement will most advantageously include a tension-adjusting link element that is readily accessible for manual adjustment. The movable member may be a coupling block that is slidably received in a forward section of a channel formed in the handle structure; the turnbuckle arrangement may also be received in the channel and accessible for adjustment through an opening extending transversely through the handle structure.
In other preferred embodiments of the frame assembly the handle structure will comprise a gripping component, having a rearward surface portion, and the blade-tensioning mechanism will include a pivotably mounted operating lever. An arm portion of the operating lever will extend upwardly against the rearward surface portion of the gripping component, in the blade-tensioning position, and will be configured to cooperate therewith to provide a comfortable hand grip for the saw assembly.